People commonly carry with them a variety of electronic devices, such as cellular phones, personal data assistants (PDA), notebook computers, digital cameras, global position system (GPS) devices, gaming devices like Game Boys and Playstation Portables, audio devices like MP3 players and iPods, and wireless email devices like Blackberries. The current trend is to converge functions like these into fewer devices that are more convenient for users. For example, cellular phones often include a digital camera function, and Blackberries often include a PDA function or a cell phone function. Notebook computers and handheld computers will soon be able to converge any of these functions and countless others.
Different devices can have very different power characteristics. For instance, a user may expect a fully charged battery to provide 4 to 6 hours of active operation in a handheld computer, 10 hours of active talk time and more than 250 hours of standby time in a cell phone, or 20 to 30 high resolution pictures in a digital camera. Ideally, when functions are converged into a single device, the device would meet the user's expectations for each function. Unfortunately, the power characteristics tend to change drastically with each added function.
For instance, in a cell phone with a high resolution digital camera function, a user may consume several minutes worth of talk time and many hours worth of standby time with each picture. After taking a few pictures, a user may be dismayed to discover that their battery is dead and no more calls can be made. Similarly, in a handheld computer with a cell phone function, the cell phone function may be rendered useless in as little as four hours by running a power hungry software application. In a handheld computer with a cell phone and a digital camera, the power characteristics become even more complicated, making the user's expectations for any one function even more difficult to meet.
One potential solution would be to use a larger battery that can provide enough power capacity to meet the user's expectations for each of the functions. Another potential solution would be to add separate batteries for each function, with each battery able to meet a user's expectation for each of the functions. Batteries, however, already account for a substantial portion of the size and shape of many devices. And, one of the most appealing aspects of converging functions is that multiple devices can be replaced with one device of about the same size and shape of a single device. So, for a multi-function device to be successful in the market place, any significant increase in battery size, or number of batteries, is likely to be out of the question.